Disease Detectives - ALL Vocabulary

age-adjusted mortality rate

A mortality rate statistically modified to eliminate the effect of different age distributions in the different populations

agent

A factor, such as a microorganism, chemical substance, or form of radiation, whose presence, excessive presence, or (in deficiency diseases) relative absence is essential for the occurrence of a disease

age-specific mortality rate

A mortality rate limited to a particular age group. The numerator is the number of deaths in that age group; the denominator is the number of persons in that age group in the population

analytic epidemiology

The aspect of epidemiology concerned with the search for health-related causes and effects. Uses comparison groups, which provide baseline data, to quantify the association between exposures and outcomes, and test hypotheses about causal relationships

analytic study

A comparative study intended to identify and quantify associations, test hypotheses, and identify causes. Two common types are cohort study and case-control study

applied epidemiology

The application or practice of epidemiology to address public health issues

association

Statistical relationship between two or more events, characteristics, or other variables

attack rate

A variant of an incident rate, applied to a narrowly defined population observed for a limited period of time, such as during an epidemic

attributable proportion

A measure of the public health impact of a causative factor; proportion of a disease in a group that is exposed to a particular factor which can be attributed to their exposure to that factor

bias

Deviation of results or inferences from the truth, or processes leading to such systematic deviation. Any trend in the collection, analysis, interpretation, publication, or review of data that can lead to conclusions that are systematically different from the truth

biologic transmission

The indirect vector-borne transmission of an infectious agent in which the agent undergoes biologic changes within the vector before being transmitted to a new host

carrier

A person or animal without apparent disease who harbors a specific infectious agent and is capable of transmitting the agent to others. The _____ state may occur in an individual with an infection that is inapparent throughout its course (known as asymptomatic ______), or during the incubation period, convalescence, and postconvalescence of an individual with a clinically recognizable disease. The _____ state may be of short or long duration (transient/chronic)

case

a countable instance in the population or study group of a particular disease, health disorder, or condition under investigation. Sometimes, an individual with the particular disease

case-control study

A type of observational analytic study. Enrollment into the study is based on presence ("case'') or absence ("control'') of disease. Characteristics such as previous exposure are then compared between cases and controls

case definition

A set of standard criteria for deciding whether a person has a particular disease or health-related condition, by specifying clinical criteria and limitations on time, place, and person

case-fatality rate

The proportion of persons with a particular condition (cases) who die from that condition. The denominator is the number of incident cases; the numerator is the number of cause-specific deaths among those cases

cause of disease

A factor (characteristic, behavior, event, etc.) that directly influences the occurrence of disease. A reduction of the factor in the population should lead to a reduction in the occurrence of disease

cause-specific mortality rate

The mortality rate from a specified cause for a population. The numerator is the number of deaths attributed to a specific cause during a specified time interval; the denominator is the size of the population at the midpoint of the time interval

chain of infection

A process that begins when an agent leaves its reservoir or host through a portal of exit, and is conveyed by some mode of transmission, then enters through an appropriate portal of entry to infect a susceptible host

class interval

A span of values of a continuous variable which are grouped into a single category for a frequency distribution of that variable

cluster

An aggregation of cases of a disease or other health-related condition, particularly cancer and birth defects, which are closely grouped in time and place. The number of cases may or may not exceed the expected number; frequently the expected number is not known

cohort

A well-defined group of people who have had a common experience or exposure, who are then followed up for the incidence of new diseases or events, as in a _____ or prospective study. A group of people born during a particular period or year is called a birth ______

cohort study

A type of observational analytic study. Enrollment into the study is based on exposure characteristics or membership in a group. Disease, death, or other health-related outcomes are then ascertained and compared

common source outbreak

An outbreak that results from a group of persons being exposed to a common noxious influence, such as an infectious agent or toxin. If the group is exposed over a relatively brief period of time, so that all cases occur within one incubation period, then the _______ _______ is further classified as a point source outbreak. In some ________ _________s, persons may be exposed over a period of days, weeks, or longer, with the exposure being either intermittent or continuous

confidence interval

A range of values for a variable of interest, e.g., a rate, constructed so that this range has a specified probability of including the true value of the variable. The specified probability is called the confidence level, and the end points of the ___________ are called the confidence limits

confidence limit

The minimum or maximum value of a confidence interval

contact

Exposure to a source of an infection, or a person so exposed

contagious

Capable of being transmitted from one person to another by contact or close proximity

contingency table

A two-variable table with cross-tabulated data

control

In a case-control study, comparison group of persons without disease

crude mortality rate

The mortality rate from all causes of death for a population

cumulative frequency

In a frequency distribution, the number or proportion of cases or events with a particular value or in a particular class interval, plus the total number or proportion of cases or events with smaller values of the variable

death-to-case ratio

The number of deaths attributed to a particular disease during a specified time period divided by the number of new cases of that disease identified during the same time period

demographic information

The "person'' characteristics--age, sex, race, and occupation--of descriptive epidemiology used to characterize the populations at risk

descriptive epidemiology

The aspect of epidemiology concerned with organizing and summarizing health-related data according to time, place, and person

determinant

Any factor, whether event, characteristic, or other definable entity, that brings about change in a health condition, or in other defined characteristics

direct transmission

The immediate transfer of an agent from a reservoir to a susceptible host by direct contact or droplet spread

distribution

In epidemiology, the frequency and pattern of health-related characteristics and events in a population. In statistics, the observed or theoretical frequency of values of a variable

droplet nuclei

The residue of dried droplets that may remain suspended in the air for long periods, may be blown over great distances, and are easily inhaled into the lungs and exhaled

droplet spread

The direct transmission of an infectious agent from a reservoir to a susceptible host by spray with relatively large, short-ranged aerosols produced by sneezing, coughing, or talking

endemic disease

The constant presence of a disease or infectious agent within a given geographic area or population group; may also refer to the usual prevalence of a given disease within such area or group

environmental factor

An extrinsic factor (geology, climate, insects, sanitation, health services, etc.) which affects the agent and the opportunity for exposure

epidemic

The occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time

epidemic curve

A histogram that shows the course of a disease outbreak or epidemic by plotting the number of cases by time of onset

epidemiologic triad

The traditional model of infectious disease causation. includes three components: an external agent, a susceptible host, and an environment that brings the host and agent together, so that disease occurs

epidemiology

The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems

evaluation

A process that attempts to determine as systematically and objectively as possible the relevance, effectiveness, and impact of activities in the light of their objectives

experimental study

A study in which the investigator specifies the exposure category for each individual (clinical trial) or community (community trial), then follows the individuals or community to detect the effects of the exposure

fomite

An inanimate intermediary in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host

frequency distribution

A complete summary of the frequencies of the values or categories of a variable; often displayed in a two column table: the left column lists the individual values or categories, the right column indicates the number of observations in each category

health

A state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity

high-risk group

A group in the community with an elevated risk of disease

histogram

A graphic representation of the frequency distribution of a continuous variable. Rectangles are drawn in such a way that their bases lie on a linear scale representing different intervals, and their heights are proportional to the frequencies of the values within each of the intervals

host

A person or other living organism that can be infected by an infectious agent under natural conditions

host factor

An intrinsic factor (age, race, sex, behaviors, etc.) which influences an individual's exposure, susceptibility, or response to a causative agent

hyperendemic disease

A disease that is constantly present at a high incidence and/or prevalence rate

active immunity

Resistance developed in response to stimulus by an antigen (infecting agent or vaccine) and usually characterized by the presence of antibody produced by the host

herd immunity

The resistance of a group to invasion and spread of an infectious agent, based on the resistance to infection of a high proportion of individual members of the group. The resistance is a product of the number susceptible and the probability that those who are susceptible will come into contact with an infected person

passive immunity

Immunity conferred by an antibody produced in another host and acquired naturally by an infant from its mother or artificially by administration of an antibody-containing preparation (antiserum or immune globulin)

incidence rate

A measure of the frequency with which an event, such as a new case of illness, occurs in a population over a period of time. The denominator is the population at risk; the numerator is the number of new cases occurring during a given time period

incubation period

A period of subclinical or inapparent pathologic changes following exposure, ending with the onset of symptoms of infectious disease

indirect transmission

The transmission of an agent carried from a reservoir to a susceptible host by suspended air particles or by animate (vector) or inanimate (vehicle) intermediaries

infectivity

The proportion of persons exposed to a causative agent who become infected by an infectious disease

interquartile range

The central portion of a distribution, calculated as the difference between the third quartile and the first quartile; this range includes about one-half of the observations in the set, leaving one-quarter of the observations on each side.

latency period

A period of subclinical or inapparent pathologic changes following exposure or symptoms, ending with the onset of symptoms of a chronic disease

measure of association

A quantified relationship between exposure and disease; includes relative risk, rate ratio, odds ratio

measure of central location

A central value that best represents a distribution of data. Includes the mean, median, and mode. Also called the measure of central tendency

measure of dispersion

A measure of the spread of a distribution out from its central value. _________ used in epidemiology include the interquartile range, variance, and the standard deviation

medical surveillance

The monitoring of potentially exposed individuals to detect early symptoms of disease

morbidity

Any departure, subjective or objective, from a state of physiological or psychological well-being

mortality rate

A measure of the frequency of occurrence of death in a defined population during a specified interval of time

necessary cause

A causal factor whose presence is required for the occurrence of the effect (of disease)

nominal scale

Classification into unordered qualitative categories; e.g., race, religion, and country of birth as measurements of individual attributes; no inherent order to their categories

normal distribution

The symmetrical clustering of values around a central location. The properties of a _______ include the following: (1) It is a continuous, symmetrical distribution; both tails extend to infinity; (2) the arithmetic mean, mode, and median are identical; and, (3) its shape is completely determined by the mean and standard deviation

nosocomial infection

infection whose development is favored by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff

observational study

Epidemiological study in situations where nature is allowed to take its course. Changes or differences in one characteristic are studied in relation to changes or differences in others, without the intervention of the investigator

odds ratio

A measure of association which quantifies the relationship between an exposure and health outcome from a comparative study; also known as the cross-product ratio

ordinal scale

Classification into ordered qualitative categories; e.g., social class (I, II, III, etc.), where the values have a distinct order, but their categories are qualitative in that there is no natural (numerical) distance between their positive values

outbreak

Synonymous with epidemic. Sometimes the preferred word, as it may escape sensationalism associated with the word epidemic. Alternatively, a localized as opposed to generalized epidemic

pandemic

An epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population

pathogenicity

The proportion of persons infected, after exposure to a causative agent, who then develop clinical disease

period prevalence

The amount of a particular disease present in a population over a period of time

point prevalence

The amount of a particular disease present in a population at a single point in time

positive predictive value

A measure of the predictive value of a reported case or epidemic; the proportion of cases reported by a surveillance system or classified by a case definition which are true cases

prevalence

The number or proportion of cases or events or conditions in a given population

prevalence rate

The proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time

propagated outbreak

An outbreak that does not have a common source, but instead spreads from person to person

public health surveillance

The systematic collection, analysis, interpretation, and dissemination of health data on an ongoing basis, to gain knowledge of the pattern of disease occurrence and potential in a community, in order to control and prevent disease in the community

rate

An expression of the frequency with which an event occurs in a defined population

relative risk

A comparison of the risk of some health-related event such as disease or death in two groups; also known as risk ratio

representative sample

A sample whose characteristics correspond to those of the original population or reference population

reservoir

The habitat in which an infectious agent normally lives, grows and multiplies; includes human, animal, and environmental

risk

The probability that an event will occur, e.g. that an individual will become ill or die within a stated period of time or age

risk factor

An aspect of personal behavior or lifestyle, an environmental exposure, or an inborn or inherited characteristic that is associated with an increased occurrence of disease or other health-related event or condition

sample

A selected subset of a population. A ____ may be random or non-random and it may be representative or non-representative

seasonality

Change in physiological status or in disease occurrence that conforms to a regular seasonal pattern

secondary attack rate

A measure of the frequency of new cases of a disease among the contacts of known cases

secular trend

Changes over a long period of time, generally years or decades

sensitivity

The ability of a system to detect epidemics and other changes in disease occurrence. The proportion of persons with disease who are correctly identified by a screening test or case definition as having disease

sentinel surveillance

A surveillance system in which a pre-arranged sample of reporting sources agrees to report all cases of one or more notifiable conditions